Highway device, in particular manhole, with frame and plug with backward movement relative to the frame to ensure the closed position of the plug in the frame

ABSTRACT

A manhole includes a frame and plug, which moves backward relative to the frame, to ensure the plug reaches a proper closed position in the frame. A first end of a self-locking arm of the structure is pivotally mounted to the frame, and can slide in a fixed guiding groove. The first end of the arm bears on a fixed stop of the frame during tilting of the plug toward the closed position of the frame. The arm moves the plug backwards and so the plug correctly closes the opening of the frame.

BACKGROUND OF THE INVENTION

The present invention relates to a highways device, in particular a manhole, comprising a rectangular frame whereof the side walls and ends delimit an opening and at least one plug whereof one side is pivotally mounted relative to an adjacent end wall of the frame by at least one joint hinge.

The invention is in particular but not exclusively applicable to manhole covers.

In such an application, the frame is durably sealed in the ground and one or several plugs articulated relative to the frame can occupy a lowered position in which the plugs cover the opening formed in said frame or a raised position in which the plugs free the opening of the frame.

Each joint hinge of a plug to the frame generally has functional play allowing the plug to be articulated to the frame without difficulty and to fit correctly into the opening of the frame delimited by its four side walls and ends to close said opening.

However, each manhole cover plug is very heavy, as it is made from a cast iron-based material, in particular spheroidal. Thus, such plugs are difficult to maneuver during tilting thereof between the closed and open positions of the frame and, moreover, when they occupy their raised open position, they can accidentally tilt to their closed position of the opening of the frame.

To resolve this problem, a safety device has already been proposed for each articulated manhole cover plug. Such a device comprises, for each manhole plug, at least one jack to assist with opening and closing the plug pivotally mounted by its ends under the plug and to the frame and a self-locking arm also articulated by its ends between the plug and the frame and making it possible to lock the plug in its upright opening position without a risk of accidental tilting of the plug towards its closed position of the frame opening.

However, such a safety device has the drawback that during tilting of the plug to its closed position of the frame opening, the assistance jack exerts a force on the plug pushing it towards the end wall of the frame opposite the joint hinge, the functional play of which risks making the corresponding edge of the plug collide with the upper edge of said end wall, thereby preventing correct closing of the frame opening by the plug and risking damaging both the edge of the plug and the corresponding end wall of the frame.

SUMMARY OF THE INVENTION

The present invention aims to offset the abovementioned drawback of the known safety devices for plugs of highways devices.

To that end, according to the invention, the highways device, in particular manhole, of the type comprising a rectangular frame whereof the side and end walls delimit an opening, at least one plug whereof one side is pivotally mounted relative to an adjacent end wall of the frame via at least one joint hinge having functional play to allow the plug to tilt between an upright position releasing the opening of the frame and a closed position of said opening while bearing on an inner peripheral seating wall of the frame and fitting into the frame, at least one jack to assist with opening or closing the plug pivotally mounted between the plug and the frame, and at least one self-locking arm pivotally mounted between the plug and the frame parallel to the assistance jack and making it possible to lock the plug in its raised position releasing the opening of the frame, is characterized in that the end of the self-locking arm is pivotally mounted to the frame able to slide in a fixed longilinear guiding groove secured to the frame and extending below the seating wall of the frame parallel to said wall so that the end of the self-locking arm can come closer to the other end wall of the frame during tilting of the plug to its closed position of the opening of the frame, in that at least one stop is secured to the frame perpendicular to the other end wall of the frame so that the sliding end of the self-locking arm bears on the stop during tilting of the plug to its closed position of the opening of the frame to cause the plug to withdraw towards the end wall adjacent to the articulated side of the plug and allow the latter to close the opening of the frame.

The self-locking arm has a determined length and is pivotally connected to a determined location of the plug so that by bearing by its sliding end on the fixed stop, it keeps the plug in a half-open safety position relative to the frame and the self-locking arm causes the plug to withdraw towards the adjacent end wall of the frame while exerting a relatively high pressure on the plug in its half-open position to bring the plug to its position closing the opening of the frame.

According to a first embodiment, the plug assumes the form of a right angled triangle and a single self-locking arm is articulated under the plug near its straight side adjacent to the side articulated to the frame and the corresponding side wall of the frame.

In this embodiment, the highways device comprises a second plug in the form of a right angled triangle whereof one of the sides is articulated relative to the other end wall of the frame by at least one joint hinge having a functional play to allow the second plug to tilt between an upright position freeing the opening of the frame and a closed position of said opening while bearing on the inner peripheral seating wall of the frame and fitting into the frame, at least one jack assisting with the opening or closing of the second plug pivotally mounted between said plug and the frame and a single self-locking arm articulated parallel to the assistance jack between the frame and under the second plug near its straight side adjacent to the side articulated to the frame and making it possible to lock said plug in its upright position freeing the opening of the frame, the self-locking arm having its end pivotally mounted to the frame able to slide in a second fixed longilinear guide groove secured to the frame and extending below the seating wall of the frame parallel to said wall so that the end of the self-locking arm can come closer to the opposite end wall of the frame during tilting of the second plug to its closed position of the opening of the frame and a second stop being secured to the frame perpendicular to the opposite end wall of the frame so that the sliding end of the self-locking arm bears on the second stop during tilting of the second plug to its closed position of the opening of the frame to cause the second plug to withdraw towards the adjacent end wall at the articulated edge of the second plug and to allow the latter to close the opening of the frame.

The two triangulated plugs make it possible to completely cover the opening of the frame in their closed position.

According to another embodiment, the plug has a rectangular shape capable of completely covering the opening of the frame in its closed position, a second self-locking arm is pivotally mounted between the plug and the frame parallel to the assistance jack and also making it possible to lock the plug in its upright position releasing the opening of the frame, the second self-locking arm having its end pivotally mounted to the frame being able to slide in a second fixed longilinear guide groove secured to the frame extending below the seating wall of the frame parallel to said wall so that the end of the second self-locking arm can come closer to the other end wall of the frame during tilting of the plug to its closed position of the opening of the frame, a second stop being secured to the frame perpendicular to the other end wall of the frame so that the sliding end of the second self-locking arm bears on the second stop during the tilting of the plug to its closed position of the opening of the frame to cause the plug to withdraw towards the end wall adjacent to the articulated side of the plug and to allow the latter to close the opening of the frame.

Each self-locking arm is articulated on one hand by one of its ends under the plug around a transverse axis of the arm and on the other hand by its opposite end sliding around a transverse axis of the arm and engaged through the corresponding guide groove to slide along said groove.

Each guide groove comprises, at its end opposite the corresponding stop, a notch for receiving the sliding axis of the self-locking arm to lock the plug in its upright position releasing the opening of the frame.

Preferably, the two self-locking arms are the same length, are arranged in two planes perpendicular to the plane of the opening edge of the frame, and are articulated by two of their ends under the plug around two coaxial axes and by their other two ends opposite the frame around two coaxial axes.

Advantageously, the device comprises two coaxial joint hinges of the plug to the frame spaced apart from each other parallel to the adjacent end wall of the frame.

Each joint hinge comprises a cylindrical axis parallel to the adjacent end wall of the frame supported by a clevis secured to the corresponding part of the seating wall of the frame and two lugs forming knuckles secured to the plug and arranged between the two branches of the clevis while being passed through by the cylindrical axis, the lugs forming knuckles having an orifice with dimensions larger than the diameter of the cylindrical axis to allow movement with play of the plug relative to the cylindrical axis.

Each stop can be adjusted in the direction perpendicular to the corresponding end wall.

Advantageously, said device comprises at least one elastically deformable means fastened to the seating wall protruding therefrom close to the end wall of the frame opposite the end wall adjacent to the joint hinge and capable of facilitating opening of the plug from its closed position of the frame.

The assistance jack is articulated on an axis secured to a platen below the seating wall of the frame.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be better understood, and other aims, features, details, and advantages thereof will appear more clearly in the following explanatory description provided in reference to the appended drawings, provided solely as an example illustrating two embodiments of the invention and in which:

FIG. 1 is a top view of a manhole according to a first embodiment of the invention where the plug is in its closed position of the frame;

FIG. 2 is a cross-sectional view along line II-II of FIG. 1;

FIG. 3 is an enlarged view of the part circled in III of FIG. 2;

FIG. 4 is an enlarged view of the part circled in IV in FIG. 2;

FIG. 5 is a cross-sectional view along line V-V of FIG. 1 and showing the plug in the half-open position relative to the frame;

FIG. 6 is an enlarged view of the part circled in VI in FIG. 5;

FIG. 7 is a perspective view of the plug of the manhole in its raised position releasing the opening of the frame;

FIG. 8 is an enlarged view of the part circled in VIII of FIG. 7;

FIG. 9 is a perspective view along arrow IX of FIG. 7;

FIG. 10 is an enlarged view of the part circled in X in FIG. 9;

FIG. 11 is a perspective bottom view of the manhole cover whereof the plug is in its closed position of the frame of said manhole;

FIG. 12 is an enlarged view of the part circled in XII in FIG. 11;

FIG. 13 is an enlarged perspective view of the part circled in XIII in FIG. 7; and

FIG. 14 is a perspective view of a second embodiment of the manhole cover according to the invention with two plugs triangulated and articulated to the frame of said manhole.

DESCRIPTION OF THE CURRENT EMBODIMENTS

The device according to the invention that will be described applies at least to a plug for a manhole cover, but it is understood that it can be applied to any plug or leaf other than that of a manhole cover.

According to the first embodiment shown in FIGS. 1 to 13, the manhole cover comprises a frame 1 with a generally rectangular shape comprising two side walls 2 and two end walls 3 welded to each other and delimiting an opening.

Each side 2 and end 3 wall constitutes one of the wings of a profile with an L-shaped transverse section, the other wing 4 of which is fastened on a sub-frame 5 via fastening bolts 6.

The wings 4 associated with the side 2 and end 3 walls protrude in the opening of the frame 1 and are arranged in a same plane to constitute a peripheral seating wall 7 of a rectangular plug 8 of the manhole cover when the plug 8 is in its closed position of the opening of the frame 1 while fitting into the opening of said frame 1.

The sub-frame 5 is intended to be partially buried in the ground of a road and is made up of a flat rectangular upper frame 9 and a lower underlying skirt 10 assembled together by welding so as to have a T-shaped transverse cross-section. The wing 4 associated with each side 2 and end 3 wall is fastened on the horizontal part forming the head of the T of the sub-frame 5 protruding in the opening of the frame 1 and outside the latter.

The sub-frame 5 is also provided with four square legs 11 respectively fastened to the four inner corners of the skirt 10.

The plug 8 is pivotally mounted by one of its sides 8 a, called rear side, to the adjacent one of the end walls 3, called rear wall, preferably by two joint hinges 12 to allow the plug 8 to tilt between an upright released position of the opening of the frame 1 and a completely closed position of the opening of said frame.

The two joint hinges 12 are arranged coaxially on the wing 4 associated with the rear wall 3 extending parallel to said rear wall.

As better emerges from FIG. 13, each joint hinge comprises a cylindrical axis 13 parallel to the rear wall and supported by a clevis 14 whereof the two parallel branches 14 a are fastened, for example by welding, on the wing 4 perpendicular thereto. The cylindrical hinge pin 13 of each hinge 12 passes through the two branches 14 a of the support clevis 14 practically without play. Each joint hinge 12 also comprise two lugs forming knuckles 15 secured to the inner face of the plug 8 near the rear edge thereof and arranged parallel between the two branches 14 a of the clevis 14 while being passed through by the cylindrical hinge pin 13.

As better emerges from FIG. 4, the orifice 16 made through each lug forming a knuckle 15 has dimensions larger than the diameter of the hinge pin 13 passing through said orifice to constitute a relatively substantial functional play of the joint hinge 12. The orifice 16 is obtained by a cast iron core and assumes the particular form in transverse cross section of FIG. 4 allowing the plug 8 to tilt between its upright position releasing the opening of the frame 1 and closing said opening without a risk of jamming of the joint hinge 12, while allowing movement of the rear edge 8 a of the plug 8 relative to the rear wall 3 as will be seen later.

Of course, the orifice 16 can have a different shape and be made up of an oblong hole once said orifice allows the rear edge 8 a of the plug 8 to move away from or closer to the corresponding rear wall 3 during tilting of the plug 8 between its open and closed positions of the frame 1.

Each hinge pin 13 is kept axial to the clevis 14 by at least one elastic ring 14 b, in this case two, fastened to each end of the axis 13 outside the corresponding branch 14 a of the clevis 14.

The two axes 13 of the hinges 12 are arranged coaxially to each other.

The plug 8 comprises, at each of its four corners, a lug 17 bearing on the peripheral seating wall 7 when the plug 8 is in its closed position of the opening of the frame 1.

The plug 8 is also provided with a lock housing 18 fastened under the plug near its front edge 8 b and the bolt 19 of which can be engaged under a strike 20 protruding from the inner face of the front end wall 3 of the frame 1 to lock the plug 8 to the frame 1 as shown in FIG. 2. The bolt 19 can be actuated to its unlocked position of the strike 20 using a key 21.

The manhole cover also comprises two parallel jacks 22 for assisting in opening or closing the plug 8 and pivotally mounted between the plug 8 and the frame 1. More specifically, one end of the body 23 of each assistance jack 22 is articulated on an axis 24 secured to a lug 25 fastened to a plate 26 protruding in the opening of the frame 1 and secured to the inner face of the corresponding skirt wall and the corresponding wing 4 associated with the rear wall 3 so that the hinge pin 24 is arranged below the wing 4 that is part of the seating wall 7 of the frame 1. The other end of the rod 27 of each jack 22 is articulated to an axis 28 secured to the end of a rib 29 protruding from the inner face of the plug 8 perpendicular thereto. The two axes 24 and 28 of each jack 22 are parallel to the hinge pins 13 of the hinges 12.

The two jacks 22 are thus respectively arranged in two planes perpendicular to the plane of the opening edge of the frame 1.

If applicable, a single assistance jack 22 can be articulated between the plug 8 and the frame 1.

The manhole cover also comprises two self-locking arms 30 each made up of a flat rigid bar and pivotally mounted between the plug 8 and the frame 1 on either side of the assistance jacks 22 parallel thereto.

One end of each self-locking arm 30 is articulated on an axis 31 supported by a lug 32 secured to the inner face of the plug 8 perpendicular thereto and situated close to the corresponding side edge 8 c of the plug 8. The two hinge pins 31 articulating the plug 8 to the two self-locking arms 30 are coaxial and parallel to the hinge pins 13 of the hinges 12. As shown, each hinge pin 31 is made up of a threaded shaft of a screw passing through the lug 32 and the end of the arm 30 and the head 33 of which bears on the side face of the lug 32 opposite that on which the end of the self-locking arm 30 bears.

The opposite end of each self-locking arm 30 is articulated on an axis 34 that passes through a fixed longilinear guiding groove 35 extending below the wing 4 and parallel thereto that is part of the seating wall 7 associated with the corresponding side wall 2 of the frame 1, this groove 35 also extending perpendicularly from the plane containing the front end wall 3 of the frame 1 over a predetermined distance corresponding to half of the length of the side wall 2. The two axes 34 of the arms 30 are coaxial and parallel to the axes 13 of the joint hinges 12.

Each groove 35 is made through a rectangular plate 36 fastened, for example by welding, opposite the corresponding wall part of the skirt 10 of the sub-frame 5 and parallel to said part while allowing a space to remain in which the head 37 of a screw constituting the axis 34 passing through the corresponding end of the self-locking arm 30 is housed.

Thus each self-locking arm 30 is arranged in a plane perpendicular to the plane of the opening edge of the frame 1 and situated close to the inner edge of the wing 4 associated with the side wall 2 of the frame 1 so that the two self-locking arms 30 can move in the opening of the of the frame 1 during tilting of the plug 8 between its open and closed positions of said frame.

Each of the grooves 35 includes, at its end opposite the front end wall 3 of the frame 1, a notch 37 for receiving the hinge pin 34 when the plug 8 is in its raised or upright position releasing the opening of the frame 1 shown in FIG. 7 so that the two self-locking arms 30 can lock the plug in said raised position.

The coaxial hinge pins 31 articulating the two self-locking arms 30 to the plug 8 are situated relative to the front edge 8 b of the plug 8 at a distance further than that separating the coaxial hinge pins 28 of the jacks 22 of said front edge.

The manhole cover also comprises two stops 38 fastened to the frame 1 while being arranged respectively in the two planes containing the two self-locking arms 30 while protruding in the opening of the frame 1 from the plane containing the front end wall 3 of said frame perpendicular to said plane. More specifically, each stop 38 is fastened to a lug 39 fastened under the horizontal branch part 9 of the T of the sub-frame 5 so that the stop 38 protrudes from two superimposed inner edges of the wing 4 associated with the front end wall 30 and the transverse branch part of the T of the sub-frame 5.

Each stop 38 can be adjusted in the direction perpendicular to the plane containing the front end wall 3 of the frame 1.

To that end and preferably, each stop 38 comprises a screw whereof the shaft 40 is anchored in its lug 39 and the head 41 protrudes in the opening of the frame 1, and a nut 42 making it possible to lock said shaft 40 in the lug 39.

The two jacks 23, the two self-locking arms 30, the two guide grooves 35 of the corresponding ends of the two self-locking arms 30, and the two stops 38 are arranged symmetrically to the vertical median plane of the frame 1 parallel to the two side walls 2 of said frame.

The manhole cover is lastly provided with at least one means 43 to help with opening the plug 8 when it is in its closed position of the opening of the frame 1.

Preferably, two means 43 for assisting with opening the plug 8 are provided and are respectively arranged in the two corners of the frame 1 defined between the front end wall 3 and the two side walls 2 of said frame and opposite the joint hinges 12.

Each means 43 is elastically deformable and protrudes from the seating wall 7 so that it is elastically compressed by the corresponding lug 17 of the plug 8 when the latter is in its closed position of the frame and is locked thereto by the bolt 19 and strike 20 assembly.

As shown in the figures, each means 43 can be made up of a rod plunger 44 secured to a circular head 45 and a helical compression spring 46 coaxially mounted around the rod 44 bearing on one hand under the head 45 and on the other hand at the bottom of a blind hole 47 made in the thickness of the seating wall part 7 and the underlying part of the head 9 of the T of said frame 5.

Thus, in the closed position of the plug 8, each of the two lugs 17 situated near the front edge 8 b of the plug 8 bears on the corresponding head 45 of the plunger means 43 to engage it, against the return force of the spring 46, in the blind hole 47 so that the outer face of the head 45 is flush with the upper face of the corresponding part of the seating wall 7.

Alternatively, each means 43 making it possible to facilitate opening of the plug 8 can be formed by a cylindrical block in an elastomer material fastened in the corresponding blind hole 47 while protruding from the upper face of the corresponding seating wall part of the frame 1 and able to be elastically compressed by the corresponding lug 17 in the closed position of the plug 8.

Of course, it is possible to provide only a single means 43 for helping to open the plug 8 by positioning it in the middle of the seating wall part 7 perpendicular to the front end wall 3 of the frame 1. In this case, the plug 8 would include an additional lug 17 arranged close to the front edge 8 b of the plug 8 between the two end lugs 17.

The operation of the manhole cover already results from the description thereof provided above and will now be explained from the closed position of the opening of the frame 1 by the plug 8.

In that position, the plug 8 is locked in the frame 1 by the bolt 19 of the lock housing 18 engaged under the strike 20 of the frame 1. The two plunger means 43 are then elastically compressed in their respective blind holes 47 by the two lugs 17 of the plug 8.

To perform the tilting operation of the plug 8 from its closed position to its open position of the frame 1, an operator unlocks the plug 8 from the frame 1 using the key 21 to disengage the bolt 19 from the strike 20. The two means forming the plunger 43 then exert a force on the plug 8 pushing said plug into a half-open position, not shown in the figures, in which the operator can easily grasp the front edge 8 b of the plug 8 as needed using a tool, to make it pivot to its upright position releasing the opening of the frame 1 shown in FIGS. 7 and 9. Of course, the jacks 22 perform their role of assisting with the opening of the plug 8 and the ends of the self-locking arms 30 slide respectively in the two grooves 35 until their two pivot axes 34 engage in their respective notches 37 to completely safely lock the plug 8 in its raised position releasing the opening of the frame 1.

Moreover, the functional play of each of the joint hinges 12 allows movement of the rear edge 8 a of the plug 8 relative to the fixed hinge pin 13 to prevent any risk of jamming during assisted tilting of the plug 8 from its closed position to its open position.

To tilt the plug 8 from its open position to its closed position of the frame 1, the operator manually disengages the two pivot axes 34 from their respective notches 37 by acting on the self-locking arms 30 to cause the pivoting, assisted by the jacks 22, of the plug 8 towards its closed position.

During this tilting, the two axes 34 slide along their respective guide grooves 35 until the lower free ends of the self-locking arms 30 bear respectively on the two stops 38. The two self-locking arms 30 have a same determined length and are pivotally connected to a determined location of the plug 8 so that by bearing on the two stops 38, they keep the plug 8 in the half-open intermediate safety position of FIG. 5.

This half-open safety position will then require the user to tilt the plug 8 to its closed position of the opening of the frame 1 by exerting a significant pressure on the plug obtained by the weight of the operator on said plug.

During tilting of the plug 8 from its half-open position of FIG. 5 to its closed position of FIG. 1, the stops 38 act on the two self-locking arms 30, which then cause the plug 8 to withdraw towards the rear end wall 3 of the frame 1 owing to the functional play between each pair of plates forming knuckles 15 and the corresponding fixed hinge pin 13 of each of the two joint hinges 12, thereby preventing the front edge 8 b of the plug 8 from colliding with the front end wall 3 of the frame 1.

In the covering position of the opening of the frame 1 by the plug 8, the two self-locking arms 30 are substantially horizontal considering the manhole cover installed in a road and the two assistance jacks 22 are slightly inclined from top to bottom in the direction of the front end wall 3 of the frame 1.

In this way, the plug 8 is correctly fitted into the opening defined by the side 2 and end 3 walls of the frame 1 in its closed position of said frame and is automatically locked to the frame 1 via the bolt 19 engaged under the strike 20.

FIG. 14 shows another embodiment of the manhole cover according to which two plugs 8 in the form of right angled triangles are articulated to the opposite sides of a rectangular frame 1 between a raised position of the plugs 8 of said figure in which the opening of the frame 1 is released and a completely closed position of the opening of said frame in which the two plugs 8 are fitted into the frame 1 with their hypotenuse walls 8 d juxtaposed and extending along a diagonal of the frame 1.

Each plug 8 is articulated by one of its straight sides 8 a relative to the corresponding so-called end wall 3 of the frame 1 by two joint hinges 12 identical to the joint hinges 12 of the first embodiment of FIGS. 1 to 13. As such, there is no point in explaining the structure of each joint hinge 12 of a triangulated plug 8 relative to the wall 3 of the frame 1, or the manner in which the components of this hinge are fastened to the plug 8 and the corresponding part of the seating wall 7.

Each triangulated plug 8 includes, under it at its apex, a lug 17 bearing, in the closed position of the plug, on the seating wall part 7 situated at the corner of the frame 1 defined between the end wall 3 opposite the joint hinges 12 of said plug and the side wall 2 adjacent to the other straight side of the triangulated plug 8 in the closed position of said plug. Although it is not shown by FIG. 14, the two diagonally opposite corners of the frame 1 in which the two lugs 17 of the two triangulated plugs 8 are respectively housed each comprise a means for helping to open each plug 8 and identical to the means 23 described in the first embodiment of the manhole cover.

Likewise, one of the two triangulated plugs 8 is equipped with a lock housing 18 having a bolt 19 able to be engaged under a strike, not shown, of the side wall 2 of the frame 1 adjacent to the side or edge 8 c of the plug 8 to lock the two plugs 8 to the frame 1 after having first lowered the other plug 8 not equipped with the lock housing 18 and then the plug 8 equipped with the lock housing 18, which locks the other plug 8 in the frame 1 via its hypotenuse wall 8 d bearing on a tab 8 e of the other plug 8 protruding transversely from its hypotenuse wall 8 d.

Each triangulated plug 8 is also equipped with two jacks 22, only one pair of which is visible for one of the plugs, and which makes it possible to assist with opening and closing the plug 8. The opposite ends of each of the assistance jacks 22 are respectively articulated under the plug 8 and to the frame 1 below hinge pins 13 of the hinges 12 in the same way as each of the assistance jacks 22 of the first embodiment such that there is no point in providing another detailed description thereof. Of course, each plug 8 may include only a single assistance jack 22.

Each of the triangulated plugs 8 is also equipped with a self-locking arm 30 only visible for one of the plugs 8 and identical to each self-locking arm 30 of the first embodiment.

Thus, one of the ends of the self-locking arm 30 of each plug 8 is articulated on a pivot axis 31 supported by a lug 32 secured to the inner face of the plug 8 perpendicular thereto and near the inner face of the wall 8 f of the plug 8 adjacent to the articulated rear side or edge 8 a of the plug 8. The opposite end of the self-locking arm 30 is articulated on an axis able to slide along a guide groove, not shown, and identical to the axis 34 and the guide groove 35 described in the first embodiment for each self-locking arm 30. Thus, the guide groove 35 is made through a rectangular plate identical to the plate 36 of the first embodiment and that is secured perpendicular to and under the seating wall part 7 adjacent to the side wall 2 of the frame 1 situated opposite the wall 8 f of the plug 8 when it is in its closed position of the frame 1. Of course, the guide groove of the corresponding end of the self-locking arm 30 of each plug 8 includes, at its end opposite its joint hinges 12, a notch as for the first embodiment making it possible to receive the pivot axis and allowing sliding of the self-locking arm to lock the plug 8 in its raised position releasing the opening of the frame 1.

As for each self-locking arm 30 of the first embodiment, the self-locking arm 30 associated with each triangulated plug 8 is arranged in a plane perpendicular to the plane of the opening edge of the frame 1 and is situated close to the inner edge of the seating wall part 7 adjacent to the side wall 2 of the frame 1.

The manhole cover of this second embodiment is also equipped with two stops respectively associated with the two triangulated plugs 8.

Each of these stops is not shown in FIG. 14, but is identical to each stop 38 of the first embodiment and is fastened in the same way as in this first embodiment.

Thus, the stop associated with the self-locking arm 30 of the plug 8 with lock housing 18 is arranged in the corner of the sub-frame 5 opposite the joint hinges 12 of said plug protruding in the opening of the frame 1 in a direction perpendicular to the end wall 3 of the other plug substantially in a same plane as that containing the self-locking arm 30 of the lock housing 18 plug.

Likewise, the stop associated with the plug 8 not including a lock housing is fastened in the corner of the frame 5 opposite the joint hinges of said plug protruding in the opening of the frame 1 in a direction perpendicular to the end wall 3 of the plug 8 including the lock housing 18 while being situated substantially in the same plane as that going through the self-locking arm 30 of the plug 8 not including a lock housing.

To bring the two triangulated panels 8 into their open position shown in FIG. 14 from their closed position of the opening of the frame 1, the operator first unlocks the bolt 19 from its strike 20 using the key, not shown, of the lock housing 18 and the two plunger means exert, on the two lugs 17 of the two plugs 8, respectively, a thrust force bringing their front apex edges 8 b of the plugs 8 into a half-open position allowing the operator to grasp and raise, if needed using a tool, first the front edge 8 b of the plug 8 with lock housing 18 to make the plug 8 pivot, with assistance from the jacks 22, to its raised position releasing the opening of the frame 1 in which it is completely safely locked by the self-locking arm 30 as for the first embodiment.

Then, the operator grasps and raises the front edge 8 b of the other triangulated plug 8 to make it pivot, with assistance from the jacks 22, to its raised position completely releasing the opening of the frame 1 to which the plug 8 is locked by the self-locking arm 30 associated therewith.

The operations tilting the two plugs 8 to their open position are facilitated by the functional play of the joint hinges 12, which thereby prevent any risk of jamming of each plug during tilting thereof in the open position.

To return the two triangulated plugs 8 to their closed position of the frame 1, the operator first disengages the lower end of the self-locking arm 30 from the notch of the corresponding guide groove associated with the plug 8 not including a lock housing and makes said plug tilt towards its closed position with the assistance of jacks associated with said plug until the end of the self-locking arm 13 bears on the corresponding stop to make it possible to immobilize the plug 8 in a half-open safety position as for the plug 8 shown in FIG. 5 of the first embodiment.

Then, the operator mounts the plug 8 to use his own weight to exert a significant force causing the plug 8 to withdraw towards the end wall 3 of the frame 1 owing to the functional play of the joint hinges adjacent to this wall so that the apex of the front edge 8 b of the plug is at least partially engaged in the corresponding corner opposite the joint hinges defined by two of the corresponding side 2 and end 3 walls with the lug 17 bearing on the plunger means that is partially compressed by the weight of the plug itself.

Then, the operator disengages the self-locking arm 30 from the other plug 8 with lock housing from the notch of its associated guide groove and makes the plug tilt towards its closed position with the assistance of jacks 22 until the end of the self-locking arm 30 bears on the corresponding stop so as to immobilize said plug in a half-open safety position.

To completely close the plug 8 with the lock housing 18, the operator mounts said plug to use his own weight to exert a substantial force thereon allowing the plug to withdraw towards the corresponding end wall 13 owing to the functional play of its joint hinges 12 and to introduce the apex of the front edge 8 equipped with said plug in the corresponding opposite corner defined between the other side 2 and end 3 walls. The lug 17 of this plug completely pushes in the associated plunger means, which simultaneously causes the other plunger means to be completely pushed in by the lug 17 of the other plug via the action exerted by the lower edge of the hypotenuse wall 8 d of the plug 8 with lock housing 18 on the tab 8 e of the other plug 8 and the two plugs are locked in their position completely closing the opening of the frame 1 via the bolt 19 engaged under its corresponding strike.

Alternatively, the two plugs 8 could be brought into their closed position by first tilting the plug 8 without lock housing to its half-open position, then the other plug 8 with lock housing 18 to its half-open position. Then, the operator, using his own weight, exerts a substantial pressure on the plug 8 with lock housing 18 so as to bring its hypotenuse wall 8 d on the tab 8 e of the other plug 8 to push the lugs 17 into their diagonally opposite respective corners of the frame 1 by compressing the plunger means and make the edges 8 a of the two plugs simultaneously withdraw towards the end walls 3 to ensure covering of the frame 1 by the two plugs without their front edges 8 b colliding with the walls 3. The two plugs 8 are then locked to the frame 1 via the bolt and strike assembly.

The presence of the two stops, the two self-locking arms respectively associated with the two triangulated plugs 8 as well as the functional play of the joint hinges of each of these two plugs to the frame 1 make it possible to ensure the tilting of each plug into the closed and open positions of the frame 1 while preventing the front apex edge 8 b of the plug from colliding with the corresponding end wall part of the frame opposite the articulations of the plug.

The fact that the frame 1 has been described as being rectangular does not limit the invention to this geometric embodiment, which also encompasses square manhole cover frames. 

1.-14. (canceled)
 15. A manhole comprising: a rectangular frame having first and second side walls and first and second end walls defining an opening in the frame, a first plug having a first side that is pivotally mounted to the first end wall of the frame; a first hinge between and hingedly connecting the first end wall of the frame and the first plug, and having play, for tilting the first plug between an upright position, providing access to the opening of the frame, and a closed position, in which the first plug bears on an inner peripheral seating wall of the frame, fitting into the frame; a first jack assisting in opening and closing of the first plug and pivotally mounted between the first plug and the frame; a first self-locking arm having first and second ends and pivotally mounted between the first plug and the frame, parallel to the first jack, for locking the first plug in the upright position, the first end of the first self-locking arm being pivotally mounted to the frame; a first linear guiding groove secured to the frame and extending below the seating wall of the frame, parallel to the seating wall; and a first stop secured to the frame, perpendicular to the second end wall of the frame, wherein: the first end of the self-locking arm is pivotally mounted to the frame and is slidable in the fixed linear guiding groove so that the first end of the self-locking arm approaches the second end wall of the frame during tilting of the first plug toward the closed position of the first plug, and the first end of the self-locking arm bears on the first stop during tilting of the first plug toward the closed position of the first plug, causing the first plug to withdraw, toward the second end wall, adjacent to a hinged side of the first plug, so the first plug closes the opening of the frame.
 16. The device according to claim 15, wherein: the first self-locking arm has a determined length and is pivotally connected at a fixed location of the first plug so that, by bearing of the sliding first end on the first stop, the first self-locking arm keeps the first plug in a half-open safety position, relative to the frame; and the first self-locking arm causes the first plug to withdraw toward the second end wall of the frame, while pressing on the first plug, in the half-open position, when the first plug is tilted toward the closing position, closing the opening of the frame.
 17. The device according to claim 15, wherein the first plug has the shape of a right triangle, and a single first self-locking arm is hinged under the first plug, near a straight side of the first plug, adjacent to a side of the first plug that is hinged to the frame, and to a corresponding one of the first and second side walls of the frame.
 18. The device according to claim 17, comprising: a second plug having the shape of a right triangle; a second hinge between and hingedly connecting the second end wall of the frame and the second plug, having play, for tilting the second plug between an upright position, providing access to the opening of the frame, and a closed position, in which the second plug bears on the seating wall of the frame, fitting into the frame; a second jack assisting with the opening and closing of the second plug, pivotally mounted between the second plug and the frame; a second self-locking arm that is hinged parallel to the second jack, located between the frame and under the second plug, near a straight side of the second plug that is adjacent to the side of the second plug that is hinged to the frame, for locking the second plug in the upright position; a second linear guiding groove secured to the frame and extending below the seating wall of the frame, parallel to the seating wall; and a second stop secured to the frame, perpendicular to the second end wall of the frame, wherein: the second self-locking arm has a first end pivotally mounted to the frame and slidable in the second fixed linear guiding groove so that the first end of the second self-locking arm approaches the second end wall of the frame during tilting of the second plug toward the closed position, and the second end of the second self-locking arm bears on the second stop during tilting of the second plug toward the closed position of the second plug, causing the second plug to withdraw, toward the second end wall, adjacent to a hinged side of the second plug so the second plug closes the opening of the frame.
 19. The device according to claim 18, wherein the first and second triangular plugs completely cover the opening of the frame in the closed positions of the first and second plugs.
 20. The device according to claim 15, wherein the first plug has a rectangular shape completely covering the opening of the frame in the closed position, and further comprising: a second self-locking arm having first and second ends and pivotally mounted between the first plug and the frame, parallel to the first jack, for locking the first plug in the upright position; a second linear guiding groove secured to the frame and extending below the seating wall of the frame, parallel to the seating wall, and a second stop secured to the frame, perpendicular to the second end wall of the frame, wherein the first end of the second self-locking arm is pivotally mounted to the frame and is slidable in the second fixed linear guiding groove so that the first end of the second self-locking arm approaches the second end wall of the frame during tilting of the first plug toward the closed position; and wherein the second end of the second self-locking arm bears on the second stop during tilting of the first plug toward the closed position, causing the first plug to withdraw, toward the second end wall, adjacent to the hinged side of the first plug so the first plug closes the opening of the frame.
 21. The device according to claim 15, wherein the first self-locking arm is hinged at the first end, under the first plug, around a transverse pin of the first self-locking arm, and the first self-locking arm, at the second end, is slidable around the transverse pin of the first self-locking arm and is engaged, through the first guiding groove, to slide along the first guiding groove.
 22. The device according to claim 21, wherein the first guiding groove comprises, at an end opposite the first stop, a notch for receiving the first self-locking arm, along the sliding pin, to lock the first plug in the upright position.
 23. The device according to claim 18, wherein the first and second self-locking arms are the same length, are arranged in respective planes that are perpendicular to an opening edge of the frame, are hinged at their respective first ends, under the first plug, around two coaxial pins, and are hinged at their respective second ends, opposite the frame, around respective coaxial pins.
 24. The device according to claim 15, further comprising first and second coaxial joint hinges connecting the first plug to the frame, spaced apart from each other, and parallel to the second end wall of the frame.
 25. The device according to claim 15, comprising: a clevis secured to part of the seating wall of the frame; and two lugs forming knuckles, secured to the first plug, and located between branches of the clevis, wherein each of the first and second joint hinges has a cylindrical axle parallel to the second end wall of the frame and is supported by the clevis, the cylindrical pins pass through the lugs, the knuckles have an orifice larger than the cylindrical pins for movement, with play, of the first plug relative to the cylindrical pins.
 26. The device according to claim 18, wherein each of the first and second stops is adjustable in a direction perpendicular to the second end wall.
 27. The device according to claim 15, further comprising at least one elastically deformable means fastened to the seating wall, protruding from the seating wall, close to the second end wall of the frame and opposite the second end wall, adjacent to the first joint hinge for facilitating moving the first plug from the closed position.
 28. The device according to claim 26, wherein the first jack is hinged to and secured to a platen below the seating wall of the frame. 